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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '790b52450f22e959ce40fefe141e06f21e14d12fa5deb5c143447fc28c56174c' 
  AND token = 'Ex3yAsph+xT5TsAQzadqWsEra3JzZzuF4jHv1UPBy9A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}